Ivan Lim's answer to Rina's Secondary 4 A Maths question.
The 24 ways you got here is just the number of ways the 4 groups (subjects) can be arranged on the shelf.
But for each of these 24 ways, within each subject the books can be further permuted.
Hence the total number of ways
= 24 x 4! x 3! x 2!
= 6921
But for each of these 24 ways, within each subject the books can be further permuted.
Hence the total number of ways
= 24 x 4! x 3! x 2!
= 6921
Oh, how careless of me! Thank you!
You are welcome.. :)
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